In an effort to ameliorate patient recovery time, many medical procedures are performed using minimally invasive techniques to access internal treatment sites. These smaller surgical fields generally require less surgical instrumentation, such as retractors, which are typically used to temporarily move neighboring tissue away from the treatment site during more invasive procedures. Obviously, this can have dire consequences if tissue proximally located to the treatment site is inadvertently damaged during surgery.
For example, one popular minimally invasive procedure to treat atrial fibrillation of the heart uses cardiac catheters through the femoral vein to the right atrium via the inferior vena cava. However, this treatment has increased risk of damaging the proximally located esophagus of the patient, in which the esophagus overlies the heart. Cardiac catheters are used to block or interfere with impulses radiating from ectopic foci inside the pulmonary veins that trigger atrial fibrillation. Electrophysiologists use cardiac catheters to ablate the heart tissue without the need for invasive open heart surgery, whereas Cardiovascular Surgeons open the chest wall to access the left atrium using an open chest procedure to effect a similar treatment. In this procedure, at least one catheter is inserted into the left atrium and is used to create a series of ablations or burns using an energy source, such as, radio-frequency (RF) energy, laser energy, ultrasound energy, cryogenics or the like. The ablations are formed around the os of the pulmonary vein and the left atrial wall of the heart. These ablations form scar tissue which does not conduct electrical impulses. Thus, the rapid and erratic impulses of atrial fibrillation are contained within the pulmonary veins by the wall of scar tissue that was formed by the ablation, and are prevented from reaching the atria and triggering it into an atrial fibrillation rhythm.
One of the most serious and, possibly fatal complications that may arise from the aforementioned procedure is an atrial-esophageal fistula (communicating hole in the posterior left atrial wall and adjacent esophagus) which is caused by thermal penetration of the walls of the atrium and esophagus by the ablation catheter. The esophagus is located at the center of the posterior mediastinum and is separated from the atrium only by the pericardial sac and/or a thin layer of fatty tissue and may be in contact with the atrium. The esophagus is supported at its upper end near the trachea and transits the diaphragm to connect with the stomach. The lower end of the esophagus is supported by the diaphragm. The thoracic portion of the esophagus between the trachea and the stomach is mobile and loosely restrained only by soft tissue, which allows the esophagus to move laterally in response to swallowing food, cardiac and lung movement, as well as upper body movements. The atrial-esophageal fistula may result, in part, from simple anatomy and the energy needed to develop ablations, as well as the design of the catheter electrode tip and other contributing factors, such as movement of the esophagus during the procedure. An atrial-esophageal fistula can lead to pericarditis (fluid between the outer wall of the heart and the pericardium) which restricts the heartbeat, causing hemorrhage, or other life threatening conditions, and sepsis which is caused by particulate matter passing from the esophagus into the left atrium and the circulatory system. When viewing these proposed ablation lesions, either pre-operatively or intra-operatively, the surgeon may be forced to change the location of some of the ablations because of the proximity to the esophagus. If a particular ablation(s) is considered necessary regardless of the location of the esophagus, the surgeon may be compelled to reduce the power to the electrode. Both of these options may result in suboptimal ablation lesions which may reduce the success rate of the procedure.
Therefore, what is needed in the art is a system and method for safely influencing and controlling the location of anatomical structure (e.g., organ) in relation to nearby tissue during a surgical procedure. In particular, the system could be used to control the location of the esophagus relative to the heart (e.g., atrium) during catheter ablation procedures.